[LLVMdev] Choosing an alias analyzer

Pranav Bhandarkar pranavb at codeaurora.org
Sat Oct 20 09:16:53 PDT 2012

Hi Duncan,

> you have to schedule SCEV alias analysis immediately before your pass.
> problem is that if a pass invalidates alias analysis information, then the
> time a pass that needs alias analysis is run then the pass manager has to
> recreate alias analysis, and when it does so the SCEV analysis is not
> recreated.  To get around this (which is what is done for TBAA and basic
> analysis if I remember right), the pass needs to be declared immutable,
> has no state, so is always valid and doesn't need to be destroyed or
> recreated.
> I doubt this is possible for the SCEV alias analysis, but I didn't look
into it.
> Yes, this is all an endless source of pain.  There's a very old PR about
> (PR3703?).
> Ciao, Duncan.
Thanks for the information.

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